In the music and computer industries, the use of optical storage media including CDs (Compact Discs) and DVDs (Digital Versatile Disc or Digital Video Disc) is well known. Read-only and read-write CDs and DVDs are presently one of the preferred means for the storage of large amounts of digital information and have considerable market acceptance. Both CDs and DVDs have different forms based on the properties of the discs, including both read-only and read-write forms. With respect to read-only CDs, these discs are referred to as CD-ROMs, read-write CDs may be referred to as CD-Rs (Compact Disc—Writeable) which include both WORM (Write Once Read Many) discs and CD-RWs (Compact Disc Re-Writeable or Write Many Read Many). With respect to DVDs, DVDs are often referred to as DVD-R and DVD-RW designating read and read-write version respectively.
As is known, the design of a read-only CD or DVD includes a circular piece of injection-molded and transparent plastic (usually polycarbonate) around 1.2 millimeters thick and having a 12 centimeter diameter. With read-only discs, the polycarbonate includes a long, tight spiral originating at the centre of the disc and having billions of tiny bumps. The bumps, when coated with an aluminum reflective layer can be read by a combined laser and opto-electric device and are interpreted as data bits. In addition to the aluminum reflective layer, the CD includes an acrylic coating of the aluminum layer and may include a label adhered to the acrylic layer. The laser is directed through the polycarbonate layer.
The recordable CD and DVD differs from the read-only media in the reflective layer and the absence of physical bumps in the polycarbonate plastic. Rather, the recordable CD or DVD includes a data layer comprising a chemical compound which may be altered to represent the light equivalent to a physical bump. WORM media utilize an organic dye which is normally reflective but when heated to a particular temperature by a laser causes a colour change, thereby optically representing a bump.
CD-RWs also use a specialized reflective layer as in the WORM media. More specifically, multiple RW technology uses a specialized compound which is an alloy of antimony, indium, silver and tellurium. This compound will undergo different phase changes when heated to different temperatures. If the compound is heated to a first lower temperature, the compound will crystallize as it cools and become reflective. If the compound is heated to a higher temperature, the compound will not crystallize as it cools and have a dull appearance. Accordingly, depending on the temperature that the media is heated to will determine whether the compound will represent a bump. Furthermore, because the chemistry does not change as result of the heating temperature, the media may be erased and re-recorded.
CD/DVD media can store upwards of 780 Mbytes of data on the conventional 12 cm disc. With such a large amount of storage capacity, it is often not required that the full available surface area be available for data storage, thereby permitting the creation of CD/DVD media having a smaller but different shape to the conventional circle. For example, discs can be shaped to a small rectangle corresponding to a business card or to almost any shape where a reasonable amount of data storage area remains on the disc.
Past techniques for shaping discs to shapes other than the standard 12 cm circle format have primarily used computer controlled shaping devices which utilize high speed rotating culling spindle to create a desired shape from a circular blank. While this technique is effective in efficiently shaping large quantities of discs, the process often damages the data storage media immediately adjacent the edge thereby affecting the visual appearance of the shaped disc as well as reducing the amount of data storage media which may lead to read and write errors with respect to any data stored thereon. This problem is particularly noted in the shaping of read-write compact discs where the data storage media is more fragile than that of a read-only CD.
With respect to recordable CD/DVD technologies, in view of the absence of physical bumps, the relative strength of adhesion of the data layer to the plastic substrate is reduced and, as a result makes shaping of the CD by conventional shaping techniques difficult. That is, traditional methods of shaping CDs results in substantial damage to the data layer beyond the immediate edge.
Accordingly, there has been a need for a system which provides an effective and efficient method of shaping discs to any desired shaped and which provides an undamaged edge on the optical discs.
More specifically, there has been a need for a method of shaping discs wherein the disc is shaped by a stamping and/or shearing process which provides a shearing pressure to the disc which results in an undamaged edge and which seals the cut edge. Still further, there has been a need for a method that enables rapid creation of shaped discs at a reasonable price.
A review of the prior art has revealed that such an apparatus or process has not been described. For example U.S. Pat. No. 5,997,788 describes a method of manufacturing CD and DVD discs in a combined molding and cutting process. U.S. Pat. No. 5,942,165 describes a process for forming irregularly shaped CDs using cutting technology. U.S. Pat. No. 5,938,989 describes a process for manufacturing optical elements from a larger disc. U.S. Pat. No. 5,882,555 discloses a method for cutting discs into non-circular shapes; U.S. Pat. No. 5,108,789 describes a method of machining discs to improve their stability utilizing a spindle; and Japanese publication 89-353059/48 describes a method of manufacturing discs which are free of burrs by using ultra violet ray curing resins.